The present invention relates generally to implantable cardiac stimulation leads, more specifically to removal of an implanted lead extending between distal and proximal ends from a body and, still more particularly, to a technique which facilitates the complete removal of the lead from the body.
Lead extraction is required when an infection occurs and at times when products are upgraded or replaced. Current lead extraction techniques cut the connector from the lead, then mechanically lock into the lead conductor coil near the lead distal electrode. During the lead extraction, the distal end of the coil is deformed and the lead is no longer functional. There is a potential for lead fracture, resulting in incomplete extraction, and possibly additional surgery to complete the procedure.
Typical of the known prior art are U.S. Pat. Nos. 5,013,310 and 5,011,482, both to Goode et al., which utilize a stylet wire which is inserted into the longitudinal passageway of an implanted lead, then secured at its distal end to the distal end of the implanted lead. Thereafter, the stylet wire is withdrawn and takes with it the implanted lead. U.S. Pat. No. 4,957,118 represents another example of the prior art in which an electrode lead is provided with a tine assembly having tines on an electrode tip which can be moved back and forth between a retracted position and an extended position. A threaded rod is rotatably mounted within the elongated body of the lead for moving the conductive electrode tip relative to the non-conductive tubular body. In a number of instances, as in U.S. Pat. No. 4,924,881 to Brewer, an implantable endocardial lead includes a retractable fixation device such as a sharpened helix. A threaded stylet passes through a lumen from a proximal end to a distal end of the lead where the stylet is screwed into a piston supporting the helix. When the helix is in an exposed position, torque can be transmitted by the stylet from the proximal end of the lead through the distal end to the piston and thence to the helix to screw the helix into the endocardial tissue. Similar constructions are disclosed in U.S. Pat. Nos. 5,129,404 and 5,593,433 to Spehr et al. and in U.S. Patent No. to Li.
It was in light of the foregoing that the present invention was conceived and has now been reduced to practice.
The present invention discloses a technique for removing an implanted lead from a body includes the steps of releasably attaching a stylet to both the distal end of the implanted lead and to the proximal end of the implanted lead. This results in a substantially unified stylet and implanted lead structure whereby withdrawal of the stylet and of the implanted lead as a unit facilitates the complete removal of the implanted lead from the body. A threaded tip end may be used for threaded engagement with a tapped bore at the distal end of the implanted lead and at the proximal end, attachment being provided by a threaded region on the stylet distant from the threaded tip end for threaded engagement with a tapped bore of a connector pin integral with the implanted lead. In this instance, the diameter of the proximal threaded region on the stylet is greater than that of the threaded tip end. In one embodiment, the implanted lead is resiliently extensible and the stylet is greater in length than the implanted lead in its relaxed condition and tension is applied to the proximal end of the implanted lead to thereby stretch it so that the proximal end of the implanted lead is generally coextensive with the proximal end of the stylet.
According to the technique, a stylet extends between distal and proximal attachment members, the distal attachment member being releasably attachable to the distal end of the implantable lead and the proximal attachment member being releasably attachable to the proximal end of the lead. This construction results in a substantially unified stylet and lead structure whereby withdrawal of the stylet and of the lead as a unit is essentially assured.
The new lead extraction method mechanically locks the stylet into the lead distal tip and the proximal end to provide force and control at the location where the lead adheres to the myocardium and creates a pulling action on the lead in addition to the force at the tip. The method also reduces the friction between the lead body and the vessel. This method stretches the lead and in the process reduces the lead body diameter. This invention will improve lead extraction in the form of fewer lead fractures, and no lead fragments left in the heart as compared to existing lead extraction systems.
Inserting the extraction stylet would not require that the lead connector be cut off. If a decision is made to abort the lead removal, the double threaded stylet can be unscrewed, leaving the lead unchanged.
In the resiliently extensible embodiment, a double threaded stylet stretches the lead during extraction by threading into both ends of the lead. The stretching is accomplished by threading the stylet into the distal end of the lead, then pulling the lead against the stylet and fixing the proximal end of the lead to the stylet. The following benefits flow from the invention:
1. the lead can be elongated, reducing the lead body diameter;
2. the lead can be pulled from the connector end and simultaneously from the distal tip in a longitudinal direction during extraction;
3. the lead will be captured between threaded sections at the distal tip and the connector pin; therefore, the lead should not fracture and certainly will be removed in its entirety; and
4. these features can be added to all implantable cardiac leads.
Three lead components, namely, the stylet, the distal tip, and the connector pin, may be different than the components typically used in cardiac leads. The stylet is threaded at the distal end of the lead for locking into the distal tip of the lead, and a second thread is proximal to where the connector pin of the lead is located when the stylet is threaded into the distal tip. The distal tip has an internal thread for the purpose of receiving the threaded stylet. The connector pin has a thread that is designed to be mated with the proximal thread on the modified stylet.
A primary feature, then, of the present invention is the provision of a technique for removal from a body of an implanted lead extending between distal and proximal ends.
Another feature of the present invention is the provision of such a technique, which facilitates the complete removal of the lead from the body.
Still another feature of the present invention is the provision of such a technique according to which a stylet extends between distal and proximal attachment members, the distal attachment member being releasably attachable to the distal end of the implantable lead and the proximal attachment member being releasably attachable to the proximal end of the lead, resulting in a substantially unified stylet and lead structure whereby withdrawal of the stylet and of the lead as a unit is essentially assured.
Yet another feature of the present invention is the provision of such a technique according to which lead extraction is achieved by mechanically engaging the distal tip and proximal connectors, eliminating the possibility of lead fracture and partial lead extraction.
Still a further feature of the present invention is the provision of such a technique according to which lead extraction can be aborted, leaving the lead unchanged.
Yet a further feature of the present invention is the provision of such a technique according to which cutting of the lead at the connector is not required as is currently required by known methods.
Still another feature of the present invention is the provision of such a technique according to which a lead and a stylet are locked together at the proximal and distal ends so that the lead can be pulled from the connector end and simultaneously from the distal tip in a longitudinal direction during extraction.
Yet another feature of the present invention is the provision of such a technique according to which the lead diameter is reduced during extraction which reduces the friction between the lead and the vessel from which it is being extracted.
Yet a further feature of the present invention is the provision of such a technique according to which a known implant method and stylet will function properly with leads incorporating the novel concept of the invention.
Other and further features, advantages, and benefits of the invention will become apparent in the following description taken in conjunction with the following drawings. It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory but are not to be restrictive of the invention. The accompanying drawings which are incorporated in and constitute a part of this invention, illustrate one of the embodiments of the invention, and together with the description, serve to explain the principles of the invention in general terms. Like numerals refer to like parts throughout the disclosure.